Prior art discloses several tamper evidency systems for containers having snap-on closures and threaded closures. For example, U.S. Pat. No. 4,646,926 to Abgay et al. shows a container finish having a lug supported by a web which extends radially outward from the finish. The lug is ramped relative to a horizontal plane. A threaded closure has saw teeth around its lowermost edge which push downward on the lug ramp when the closure is installed. A vertical edge of a saw tooth engages a vertical edge of the lug when the closure is unscrewed. Unscrewing cannot occur without shearing off the lug. Since the lug is visible and accessible below the closure, the consumer can determine if it is missing, indicating potential tampering. Unfortunately, when a tamper evidency feature such as Abgay et al.'s lug is accessible, it is also capable of being manually overridden. Therefore, it is unreliable as a tamper evidency system.
U.S. Pat. No. 4,669,124 to Kimura discloses a threaded closure which has outwardly extending saw teeth. A frangible engagement member is located outside the closure. The arrangement is like a ratchet and pawl. The frangible member bends radially outward as the saw teeth pass it when the closure is installed. Upon unscrewing the closure, the frangible member is pushed circumferentially and it is sheared off. As with Abgay et al. the external location of the frangible member allows it to be manually bent to avoid the shearing forces. Thus, Kimura also fails to provide a reliable tamper evidency system.
U.S. Pat. No. 3,888,383 to Rowlands discloses a container having a threaded closure which has a radially inward projecting tooth. When the closure is installed, the tooth cams downward a pull tab, attached to the container finish, to where the pull tab is visible and accessible. The tooth then passes the pull tab. Upon attempting to unscrew the closure, the tooth engages the pull tab and prevents the closure from being unscrewed. The pull tab must first be manually ripped off the container finish before the closure can be opened. This system cannot be easily overridden and is therefore reliable. However, the need to grip a pull tab and pull it off may be difficult for some users, especially the elderly with arthritis.
Tamper evidency members, such as the pull tab of Rowlands, which are molded integrally with plastic containers, are often difficult to remove. The size of the connection to the container is directly related to the rate of plastic flow to the member which is intended to be pulled or twisted or otherwise sheared off at the connection point. A very small connection point which is easy to shear may require excessive time to form in a molding system. A large connection may be rapidly molded but require excessive force to remove from the container.
There is a need for a tamper evidency system which enables the user to grip the closure in order to remove the tamper evidency member, yet have a member which is not readily accessible so that the reliability of the system is preserved.
There is also a need to provide a leverage means for reducing the force to remove a tamper evidency member which has been integrally molded either with a container or a closure.